U.S. patent application number 10/629482 was filed with the patent office on 2004-04-15 for functionalized periodic mesoporous materials, their synthesis and use.
This patent application is currently assigned to ExxonMobil Research and Engineering Company. Invention is credited to Asefa, Tewodros, Ozin, Geoffrey A..
Application Number | 20040072674 10/629482 |
Document ID | / |
Family ID | 32073270 |
Filed Date | 2004-04-15 |
United States Patent
Application |
20040072674 |
Kind Code |
A1 |
Ozin, Geoffrey A. ; et
al. |
April 15, 2004 |
Functionalized periodic mesoporous materials, their synthesis and
use
Abstract
A functionalized porous crystalline material is disclosed
exhibiting an X-ray diffraction pattern with at least one peak at a
position greater than about 1.8 nm d-spacing with a relative
intensity of 100. The crystalline material comprises a framework
including metal atoms, oxygen atoms and at least one organic group
bonded between at least two of said metal atoms so as to be
integral with said framework, and wherein said organic group has at
least one sulfonate moiety bonded thereto.
Inventors: |
Ozin, Geoffrey A.; (Toronto,
CA) ; Asefa, Tewodros; (Montreal, CA) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P.O. Box 900
Annandale
NY
08801-0900
US
|
Assignee: |
ExxonMobil Research and Engineering
Company
|
Family ID: |
32073270 |
Appl. No.: |
10/629482 |
Filed: |
July 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60405509 |
Aug 23, 2002 |
|
|
|
Current U.S.
Class: |
502/60 |
Current CPC
Class: |
B01J 31/0212 20130101;
B01J 29/0308 20130101; B01J 31/0215 20130101 |
Class at
Publication: |
502/060 |
International
Class: |
B01J 029/04; B01J
029/87 |
Claims
What is claimed is:
1. A functionalized porous crystalline material exhibiting an X-ray
diffraction pattern with at least one peak at a position greater
than about 1.8 nm d-spacing with a relative intensity of 100,
wherein said crystalline material comprises a framework including
metal atoms, oxygen atoms and at least one organic group bonded
between at least two of said metal atoms so as to be integral with
said framework, and wherein said organic group has at least one
sulfonate moiety bonded thereto.
2. The porous crystalline material of claim 1, wherein said metal
atoms are selected from silicon, germanium, tin, boron and mixtures
thereof.
3. The porous crystalline material of claim 1, wherein said metal
atoms are silicon.
4. The porous crystalline material of claim 1, wherein said organic
group is selected from an alkylene group, alkenylene group, a
vinylene group, an alkynylene group, a phenylene group and a
hydrocarbon containing a phenylene group.
5. The porous crystalline material of claim 1, wherein said organic
group is an alkylene group having 1 to 6 carbon atoms and said
metal atoms are attached to the same carbon atom or to adjacent
carbon atoms.
6. A process for producing the inorganic, porous crystalline
material of claim 1, comprising the step of polycondensing an
organometallic compound in the presence of a surfactant, wherein
the organometallic compound includes an organic group bonded to at
least two metal atoms and at least two hydrolysable groups bonded
to each of said metal atoms and wherein said organic group has at
least one sulfur-containing moiety bonded thereto.
7. The process of claim 6 wherein three hydrolysable groups bonded
to each of said metal atoms.
8. The process of claim 6 wherein the at least one
sulfur-containing moiety is a sulfonate moiety.
9. The process of claim 6 wherein the at least one
sulfur-containing moiety is a precursor to a sulfonate moiety and
the process includes the additional step of converting said
precursor to a sulfonate moiety.
10. The process of claim 6 wherein the organometallic compound has
the formula: (R.sup.2.sub.mR.sup.3.sub.nM).sub.x-R wherein M is a
metal atom; R.sup.1 is a hydrocarbyl group having at least one
sulfur-containing moiety, with the metal atoms M being connected to
the same carbon atom or to adjacent carbon atoms; R.sup.2 is a
hydrolysable group, such as an alkoxy group or a halide; R.sup.3 is
a hydrocarbyl group or hydrogen; m is an integer of at least 2; n
is an integer of 0 or more obtained by subtracting (m+1) from the
valency of the metal atom M; and x is an integer of at least 2.
11. The process of claim 10 wherein said hydrocarbyl group is a
C1-C6 hydrocarbyl group.
12. The process of claim 6 wherein said surfactant has the formula
R.sub.1R.sub.2R.sub.3R.sub.4Q.sup.+ wherein Q is nitrogen or
phosphorus and wherein at least one of R.sub.1, R.sub.2, R.sub.3
and R.sub.4 is aryl or alkyl group of from about 6 to about 36
carbon atomsf, the remainder of R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 being selected from hydrogen, alkyl of from 1 to 5 carbon
atoms and combinations thereof.
13. The process of claim 6 wherein said surfactant is selected from
cetyltrimethylammonium, cetyltrimethylphosphonium,
decyltrimethylammonium octadecyltrimethylammonium,
octadecyltrimethylphosphonium, cetylpyridinium,
benzyltrimethylammonium and dimethyldidodecylammonium cations.
14. The process of claim 6 wherein the molar ratio of
organometallic compound to surfactant is between 1:0.12 and
1:0.24
15. The process of claim 6 wherein the molar ratio of
organometallic compound to surfactant is between 1:0.12 and 1:0.18.
Description
[0001] This application claims the benefit of U.S. Provisional
application 60/405,509 filed Aug. 23, 2002.
BACKGROUND OF THE INVENTION
[0002] This invention relates to functionalized periodic mesoporous
materials and to their synthesis and use.
[0003] Porous inorganic solids have found great utility as
catalysts and separations media for industrial application. The
openness of their microstructure allows molecules access to the
relatively large surface areas of these materials that enhance
their catalytic and sorptive activity. Until recently, porous
materials were generally divided into three broad categories using
the details of their microstructure as a basis for classification.
These categories are the amorphous and paracrystalline supports,
the crystalline molecular sieves and modified layered materials.
The detailed differences in the microstructures of these materials
manifest themselves as important differences in the catalytic and
sorptive behavior of the materials, as well as in differences in
various observable properties used to characterize them, such as
their surface area, the sizes of pores and the variability in those
sizes, the presence or absence of X-ray diffraction patterns and
the details in such patterns, and the appearance of the materials
when their microstructure is studied by transmission electron
microscopy and electron diffraction methods.
[0004] Amorphous and paracrystalline materials represent an
important class of porous inorganic solids that have been used for
many years in industrial Typical examples of these materials are
the amorphous silicas commonly used in catalyst formulations and
the paracrystalline transitional aluminas used as solid acid
catalysts and petroleum reforming catalyst supports. The term
"amorphous" is used here to indicate a material with no long range
order and can be somewhat misleading, since almost all materials
are ordered to some degree, at least on the local scale. An
alternate term that has been used to describe these materials is
"X-ray indifferent". The microstructure of the silicas consists of
100-250 Angstrom particles of dense amorphous silica (Kirk-Othmer
Encyclopedia of Chemical Technology, 3rd Edition, Vol. 20, John
Wiley & Sons, New York, p. 766-781, 1982), with the porosity
resulting from voids between the particles. Since there is no long
range order in these materials, the pores tend be distributed over
a rather large range. This lack of order also manifests itself in
the X-ray diffraction pattern, which is usually featureless.
[0005] Paracrystalline materials, such as certain aluminas, also
have a wide distribution of pore sizes, but tend to exhibit better
defined X-ray diffraction patterns usually consisting of a few
broad peaks. The microstructure of these materials consists of tiny
crystalline regions of condensed alumina phases, with the porosity
of the materials resulting from irregular voids between these
regions (K. Wefers and Chanakya Misra, "Oxides and Hydroxides of
Aluminum", Technical Paper No. 19 Revised, Alcoa Research
Laboratories, p. 54-59, 1987). Since, there is no long range order
controlling the sizes of pores in the material, the variability in
pore size is typically quite high. The sizes of pores in these
materials fall into a regime called the mesoporous range which, for
the purposes of this application, is from about 2 to about 50
nm.
[0006] In sharp contrast to these structurally ill-defined solids
are materials whose pore size distribution is very narrow because
it is controlled by the precisely repeating crystalline nature of
the materials' microstructure. These materials are called
"molecular sieves", the most important examples of which are
zeolites.
[0007] Zeolites, both natural and synthetic, have been demonstrated
in the past to have catalytic properties for various types of
hydrocarbon conversion. Certain zeolitic materials are ordered,
porous crystalline aluminosilicates having a definite crystalline
structure as determined by X-ray diffraction, within which there
are a large number of smaller cavities which may be interconnected
by a number of still smaller channels or pores. These cavities and
pores are uniform in size within a specific zeolitic material.
Since the dimensions of these pores are such as to accept for
adsorption molecules of certain dimensions while rejecting those of
larger dimensions, these materials are known as "molecular sieves"
and are utilized in a variety of ways to take advantage of these
properties.
[0008] Such molecular sieves, both natural and synthetic, include a
wide variety of positive ion-containing crystalline silicates.
These silicates can be described as a rigid three-dimensional
framework of Periodic Table Group IVB element oxide, e.g.
SiO.sub.4, and Periodic Table Group IIIB element oxide, e.g.
AlO.sub.4, in which the tetrahedra are cross-linked by the sharing
of oxygen atoms whereby the ratio of the total Group IIIB element,
e.g. aluminum, and Group IVB element, e.g. silicon, atoms to oxygen
atoms is 1:2. The electrovalence of the tetrahedra containing the
Group IIIB element is balanced by the inclusion in the crystal of a
cation, for example, an alkali metal or an alkaline earth metal
cation. This can be expressed wherein the ratio of the Group IIIB
element to the number of various cations, such as Ca/2, Sr/2, Na, K
or Li, is equal to unity. One type of cation may be exchanged
either entirely or partially with another type of cation utilizing
ion exchange techniques in a conventional manner. By means of such
cation exchange, it has been possible to vary the properties of a
given silicate by suitable selection of the cation.
[0009] The precise crystalline microstructure of most zeolites
manifests itself in a well-defined X-ray diffraction pattern that
usually contains many sharp maxima and that serves to uniquely
define the material. Similarly, the dimensions of pores in these
materials are very regular, due to the precise repetition of the
crystalline microstructure. All molecular sieves discovered to date
have pore sizes in the microporous range, which is usually quoted
as 0.2 to less than 2.0 nm, with the largest reported being about
1.3 nm.
[0010] Certain layered materials, which contain layers capable of
being spaced apart with a swelling agent, may be pillared to
provide materials having a large degree of porosity. Examples of
such layered materials include clays which may be swollen with
water, whereby the layers of the clay are spaced apart by water
molecules. Other layered materials are not swellable with water,
but may be swollen with certain organic swelling agents such as
amines and quaternary ammonium compounds. Examples of such
non-water swellable layered materials are described in U.S. Pat.
No. 4,859,648 and include layered silicates, magadiite, kenyaite,
trititanates and perovskites. Another example of a non-water
swellable layered material, which can be swollen with certain
organic swelling agents, is a vacancy-containing titanometallate
material, as described in U.S. Pat. No. 4,831,006.
[0011] Once a layered material is swollen, the material may be
pillared by interposing a thermally stable substance, such as
silica, between the spaced apart layers. The aforementioned U.S.
Pat. Nos. 4,831,006 and 4,859,648 describe methods for pillaring
the non-water swellable layered materials described therein and are
incorporated herein by reference for definition of pillaring and
pillared materials. Other patents teaching pillaring of layered
materials and the pillared products include U.S. Pat. Nos.
4,216,188; 4,248,739; 4,176,090; and 4,367,163; and European Patent
Application 205,711.
[0012] The X-ray diffraction patterns of pillared layered materials
can vary considerably, depending on the degree that swelling and
pillaring disrupt the otherwise usually well-ordered layered
microstructure. The regularity of the microstructure in some
pillared layered materials is so badly disrupted that only one peak
in the low angle region on the X-ray diffraction pattern is
observed, at a d-spacing corresponding to the interlayer repeat in
the pillared material. Less disrupted materials may show several
peaks in this region that are generally orders of this fundamental
repeat. X-ray reflections from the crystalline structure of the
layers are also sometimes observed. The pore size distribution in
these pillared layered materials is narrower than those in
amorphous and paracrystalline materials but broader than that in
crystalline framework materials.
[0013] More recently, a new class of porous materials has been
discovered, see U.S. Pat. No. 5,102,643, and has been the subject
of intensive scientific research. This class of new porous
materials, referred to as the M41S materials, may be classified as
periodic mesoporous materials and comprise an inorganic porous
crystalline phase material having pores with a diameter of 1.5 to
30 nm, which is larger than known zeolite pore diameters. The pore
size distribution is generally uniform and the pores are regularly
arranged. The pore structure of such mesoporous materials is large
enough to absorb large molecules and the pore wall structure can be
as thin as about 1 nm. Further, such mesoporous materials are known
to have large specific surface areas (about 1000 M.sup.2/g) and
large pore volumes (about 1 cc/g). For these reasons, such the
mesoporous materials enable reactive catalysts, adsorbents composed
of a functional organic compound and other molecules to rapidly
diffuse into the pores and are therefore, advantageous over
zeolites, which have smaller pore sizes. Consequently, such
mesoporous materials find potential high-speed catalytic reactions
and as large capacity adsorbents.
[0014] One problem with existing periodic mesoporous materials is
that the relative inactivity of the materials limits their utility
in catalytic reactions. Various proposals have therefore been made
to enhance their activity by functionalizing the materials.
[0015] For example, U.S. Pat. No. 5,145,816 discloses
functionalization of periodic mesoporous materials by
post-synthesis treatment with a composition comprising M'X'Y'n
wherein M' is selected from Periodic Table Groups IIA, IIIA, IVA,
VA, VIA, VIIIA, IB, IIB, IIIB, IVB, VB and VIB; X' is selected from
halides, hydrides, alkoxides of 1 to about 6 carbon atoms, alkyl of
C.sub.1-18, alkenyl of C.sub.1-18, aryl of C.sub.1-18, aryloxide of
C.sub.1-18, sulfonates, nitrates and acetates; Y' is selected from
a group consisting of X', amines, phosphines, sulfides, carbonyls
and cyanos; and n=1-5. However, post-synthesis functionalization is
often accompanied by substantial deceases in pore diameter and pore
volume.
[0016] PCT Publication No. WO9834723 describes attaching organic
groups onto the surface of the inorganic skeleton of periodic
mesoporous materials, namely onto the inner surface of the pores,
so as to impart selective adsorption ability and specific catalyst
functions to the mesoporous substance. Such mesoporous materials
are formed with organic groups bound as side chains suspended from
the surface of the inorganic base skeleton. Consequently, the pore
wall is basically composed of an inorganic skeleton with the
organic groups projecting from the surface of the pore wall to form
a layer composed of the organic groups.
[0017] In such a structure, the surface characteristics of the
porous material are determined by the characteristics of the
organic groups. As a result, such porous materials are restricted
to adsorbing substances to which the organic groups have
affinities. Further, the catalytic function or adsorption function
derived from the inorganic skeleton can be masked, because the
catalytically active sites or adsorption sites in the inorganic
skeleton are covered by the organic groups. In addition, the
thickness of the pore wall also may increase corresponding to the
introduction of the organic group, thereby resulting in substantial
decreases in pore diameter and pore volume of the molecular sieve.
Further, such organic groups may release under high temperatures or
in a catalytic reaction and adsorption process, thus leading to the
loss of desirable surface properties and the contamination of the
treated material by the released organic group.
[0018] In an attempt to alleviate the shortcomings of surface
attachment of organic groups, U.S. Pat. No. 6,248,686, which is
incorporated herein by reference, teaches incorporating an organic
group into the skeleton of a mesoporous material. More
specifically, the patent teaches incorporation of an organic group
into the mesoporous skeleton such that the organic group is bound
to at least two metal atoms in the skeleton. It is reported that
the inclusion of the organic group into the skeleton of the
mesoporous material confers the properties of the organic group on
the mesoporous material without substantially reducing its pore
diameter or pore volume. Among the organic groups disclosed in the
'686 patent are alkylene groups, alkenylene groups, vinylene
groups, alkynylene groups, phenylene groups, hydrocarbons
containing phenylene groups, amido groups, amino groups, imino
groups, mercapto groups, sulfone (.dbd.SO.sub.2) groups, carboxyl
groups, ether groups and acyl groups.
[0019] According to the present invention, a new class of solid
acid periodic mesoporous materials have been discovered in which
the materials have bridging organic groups containing sulfonic acid
moities incorporated into the framework. The resulting sulfonic
acid functionalized mesoporous materials have rigid, accessible,
reactive and uniformly distributed acid groups and exhibit chemical
and physical properties suggesting potential utility in
heterogeneous catalysis.
SUMMARY
[0020] In one aspect, the present invention resides in a
functionalized porous crystalline material exhibiting an X-ray
diffraction pattern with at least one peak at a position greater
than about 1.8 nm d-spacing with a relative intensity of 100,
wherein said crystalline material comprises a framework including
metal atoms, oxygen atoms and at least one organic group bonded
between at least two of said metal atoms so as to be integral with
said framework, and wherein said organic group has at least one
sulfonate moiety bonded thereto.
[0021] Conveniently, said metal atoms are selected from silicon,
germanium, tin, boron and mixtures thereof. Typically, the at least
two metal atoms are silicon.
[0022] Conveniently, the organic group is selected from an alkylene
group, alkenylene group, a vinylene group, an alkynylene group, a
phenylene group and a hydrocarbon containing a phenylene group. In
one practical embodiment, the organic group is an alkylene group
having 1 to 6 carbon atoms, with the metal atoms being connected to
the same or adjacent carbon atoms.
[0023] In a further aspect, the invention resides in a process for
producing an functionalized porous crystalline material according
to said one aspect of the invention comprising the step of
polycondensing an organometallic compound in the presence of a
surfactant, wherein the organometallic compound includes an organic
group bonded to at least two metal atoms and at least two
hydrolysable groups bonded to each of said metal atoms and wherein
said organic group has at least one sulfur-containing moiety bonded
thereto.
[0024] Conveniently, the at least one sulfur-containing moiety is a
sulfonate moiety.
[0025] Alternatively, the at least one sulfur-containing moiety is
a precursor to sulfonate moiety and the process includes the
additional step of converting said precursor to a sulfonate
moiety.
DESCRIPTION OF THE DRAWINGS
[0026] FIGS. 1(a) to (e) are X-ray diffraction patterns of the
functionalized periodic mesoporous products of Examples 3, 4, 5, 8
and 10 respectively.
[0027] FIG. 2 is the 13C CP-MAS NMR spectrum of the functionalized
periodic mesoporous product of Example 3.
[0028] FIGS. 3(a) and (b) are the .sup.13C CP-MAS NMR spectra of
the periodic mesoporous product of Example 4, after and before
respectively oxidation with hydrogen peroxide.
[0029] FIGS. 4(a) and (b) are the .sup.13C CP-MAS NMR spectra of
the periodic mesoporous product of Example 5, after and before
respectively oxidation with hydrogen peroxide.
[0030] FIGS. 5(a) and (b) are the .sup.13C CP-MAS NMR spectra of
the periodic mesoporous product of Example 8, after and before
respectively oxidation with hydrogen peroxide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] The present invention provides a novel functionalized
periodic mesoporous material exhibiting an X-ray diffraction
pattern with at least one peak at a position greater than about 1.8
nm d-spacing (4.909 degrees two-theta for Cu K-alpha radiation)
with a relative intensity of 100 and having uniformly-sized pores
typically having a diameter (maximum perpendicular cross-sectional
pore dimension) of about 1.5 nm or greater as measured by
physisorption measurements. Typically, the material will have a
hexagonal arrangement of such uniformly-sized pores.
[0032] The X-ray diffraction data employed herein were collected on
a Siemens D5000 diffractometer employing a high power Ni-filtered
Cu--K.sub..alpha. radiation with a wavelength of 0.154178 nm
operating at 50 kV/35 mA.
[0033] The mesoporous material of the present invention comprises a
crystalline framework including metal atoms, oxygen atoms and at
least one organic group which is bonded between at least two of
said metal atoms so as to be integral with the framework and which
has at least one sulfonate moiety bonded thereto.
[0034] Various metal atoms may be utilized in the crystal
framework, such as silicon, germanium, tin, boron and mixtures
thereof. Typically, the crystal framework will contain silicon
atoms so that, for example, the material may comprise --Si--O--
bonds.
[0035] The at least one organic group is integrated into framework
of the mesoporous material during synthesis so that the framework
has a hybrid composition composed of organic and inorganic
material. Consequently, the organic group is held within the
mesoporous material in a stable manner. Further, because the
organic group is integrated into the pore wall instead of being
suspended from the surface of the pore wall, the pore diameter and
pore volume of the material are not substantially reduced by the
incorporation of the organic species.
[0036] The organic group comprises a hydrocarbyl moiety to which is
bonded a sulfonate moiety. Suitable hydrocarbyl moieties include an
alkylene group, an alkenylene group, a vinylene group, an
alkynylene group, a phenylene group and a hydrocarbyl group
containing a phenylene group. Where the hydrocarbyl moiety is an
alkylene group, the group will typically have 1 to 6 carbon atoms,
such as 1 to 4 carbon atoms, with the metal atoms being connected
to the same carbon atom or to adjacent carbon atoms.
[0037] Examples of suitable hydrocarbyl moieties include, but are
not limited to, a methylene group (--CH.sub.2--), an ethylene group
(--CH.sub.2CH.sub.2--), a 1,2-butylene group
(--CH(C.sub.2H.sub.5)CH.sub.- 2--), a 2,3-butylene group
(--CH(CH.sub.3)CH(CH.sub.3)--) and a phenylene group
(--C.sub.6H.sub.4--). It will be appreciated that in the mesoporous
material of the invention, at least one hydrogen atom in the
hydrocarbyl moiety is substituted by a sulfonate moiety
(--SO.sub.3H) so that, in the case of a methylene moiety, the
framework organic group is --CH SO.sub.3H.sup.-.
[0038] By virtue of being anchored to a rigid and short bridging
organic group synthesized into the framework of the mesoporous
material, the sulfonate moiety is rigidly secured, accessible,
reactive and uniformly distributed in the material. Moreover, the
acidic nature of the sulfonate group should render the mesoporous
material of the invention useful in heterogeneous acid catalyzed
reactions, such as esterification, alcohol dehydration,
condensation, alkylation, transalkylation, isomerization,
oligomerization, acylation and nitration.
[0039] The functionalized periodic mesoporous material of the
invention is conveniently synthesized by polycondensation of an
organometallic compound in the presence of a surfactant. The
organometallic compound includes an organic group bonded to at
least two metal atoms and at least two, and preferably three,
hydrolysable groups bonded to each of said metal atoms, wherein the
organic group has at least one sulfur-containing moiety bonded
thereto. Conveniently, the at least one sulfur-containing moiety is
a sulfonate moiety. Alternatively, the at least one
sulfur-containing moiety is a precursor to sulfonate moiety and the
process includes the additional step of converting said precursor
to a sulfonate moiety.
[0040] Suitable organometallic compounds for use in the synthesis
of the mesoporous material of the invention have the formula:
(R.sup.2.sub.mR.sup.3.sub.nM).sub.x-R.sup.1
[0041] wherein
[0042] M is a metal atom;
[0043] R.sup.1 is a hydrocarbyl group, such as C1-C6 hydrocarbyl
group, having at least one sulfur-containing moiety, wherein the
metal atoms M are connected to the same or adjacent carbon
atoms;
[0044] R.sup.2 is a hydrolysable group, such as an alkoxy group or
a halide;
[0045] R.sup.3 is a hydrocarbyl group or hydrogen;
[0046] m is an integer of at least 2;
[0047] n is an integer of 0 or more obtained by subtracting (m+1)
from the valency of the metal atom M; and
[0048] x is an integer of at least 2.
[0049] One suitable organometallic compound is
bis(triethoxysilyl)methylth- iol, in which M is silicon, R.sup.1 is
a methinethiol group (.ident.CSH), R.sup.2 is an ethoxy group, m is
3, n is 0 and x is 2. Such an organometallic compound can readily
be synthesized from commercially available
bis(triethoxysilyl)methane by lithiation followed by (a) reaction
with elemental sulfur, or (b) reaction with bromine and then with
either KHS.xH.sub.2O or with H.sub.2S/KOH. The thiol group can be
converted to the desired sulfonate moiety by treatment with
hydrogen peroxide either before or after the polycondensation
reaction. Alternatively, the bis(triethoxysilyl)methyl lithium
obtained by lithiation of bis(triethoxysilyl)methane can be
directly converted to the sulfonate analog by reaction with, for
example, trimethylamine sulfur trioxide complex.
[0050] Another suitable organometallic compound is
bis(triethoxysilyl)buty- lthiol which can readily be synthesized
from bis(triethoxysilyl)methane by lithiation followed by reaction
with 3-chloro-1-propanethiol.
[0051] The surfactant used in the synthesis of the mesoporous
material of the invention is a quaternary ammonium or phosphonium
ion of the formula R.sub.1R.sub.2R.sub.3R.sub.4Q.sup.+ wherein Q is
nitrogen or phosphorus and wherein at least one of R.sub.1,
R.sub.2, R.sub.3 and R.sub.4 is aryl or alkyl group of from about 6
to about 36 carbon atoms, e.g. --C.sub.6H.sub.13,
--C.sub.10H.sub.21, --C.sub.16H.sub.33 and --C.sub.18H.sub.37 or
combinations thereof, the remainder of R.sub.1, R.sub.2, R.sub.3
and R.sub.4 being selected from hydrogen, alkyl of from 1 to 5
carbon atoms and combinations thereof. Non-limiting examples of
these surfactants include cetyltrimethylammonium,
cetyltrimethylphosphoni- um, decyltrimethylammonium
octadecyltrimethylammonium, octadecyltrimethylphosphonium,
cetylpyridinium, benzyltrimethylammonium, and
dimethyldidodecylammonium. The compound from which the above
quaternary ammonium or phosphonium ion is derived may be, for
example, the hydroxide, halide, or silicate.
[0052] The polycondensation reaction is conveniently effected by
mixing the organometallic compound and the surfactant in a suitable
solvent, such as water, then adding an acid or alkali to the
mixture. Preferably, the polycondensation reaction is conducted at
a pH of less than 7. The molar ratio of organometallic compound to
surfactant in the mixture is suitably between 1:0.12 and 1:0.24
although, for the synthesis of hexagonally ordered materials, the
molar ratio of organometallic compound to surfactant is more
typically between 1:0.12 and 1:0.18. The mixture is maintained at a
temperature of 25 to 80.degree. C., such as 60 to 80.degree. C.,
with or without stirring, for sufficient time, such as from 12
hours to 7 days, to allow the polycondensation to proceed. The
product is then recovered by filtration, then washed and dried. The
surfactant can be removed from the mesoporous product by solvent
extraction, such as with a methanol/HCl mixture.
[0053] The invention will now be more particularly described with
reference to the following Examples.
[0054] In the Examples, solution phase NMR spectra were taken with
a Varian VXR 300 spectrometer using tetramethylsilane as an
internal reference. Solid state .sup.13C CP-MAS NMR spectra were
acquired on a Bruker DSX 400 spectrometer using a zirconia rotor
containing the samples and spinning at 6.5 KHz and operating at a 3
second recycle delay, 2 microsecond contact time, .pi./2 pulse
width of 4.5-7.0 .mu.s and 3000-5000 scans.
EXAMPLE 1
Synthesis of [bis(triethoxysilyl)methyl]lithium salt
[0055] A commercially available bis(triethoxysilyl)methane (BTM)
was lithiated by the following procedure. To 300 mL of freshly
distilled dry tetrahydrofuran (THF) in a 3-neck flask attached to a
bubbler was added 3.07 g (9.00 mmol) BTM and the solution was
flushed for 5 minutes with nitrogen that had been passed through a
drying column packed with CaCl.sub.2 and Drierite. The solution was
cooled down to -78.degree. C. and then 5.2 mL, 1.7 M (9 mmol) of
t-butyllithium was added dropwise over 10 minutes. The solution was
stirred for 30 minutes at -78.degree. C. after which a very, faint
yellowish solution resulted. Then the temperature of the solution
was raised to room temperature (RT) and stirring continued for 30
minutes at RT after which the solution turned colorless.
EXAMPLE 2
Coupling of [bis(triethoxysilyl)methyl]lithium with sulfur
[0056] The carbanion solution produced in Example 1 was cooled to
-78.degree. C. and quenched with a tetrahydofuran (THF, 100 mL)
solution of 0.29 g of sulfur (1.13 mmol S.sub.8 or 9.04 mmol S
atoms) over 10 minutes under nitrogen. Stirring continued at
-78.degree. C. for 30 minutes and then at RT for 24 hrs and the
color of the solution turned deep yellowish. Then 0.29 g (9.06
mmol) of MeOH (or alternatively 9 mL, 1 M HCl/Ethanol) was added to
the solution and stirring continued for 5 minutes. After extraction
of the solvent, a brownish solution was obtained. The crude
product, lithium bis(triethoxysilyl)methyl sulfide, was
characterized by NMR: .sup.1H NMR (300 MHz, CDCl.sub.3) .delta.
1.25 (t, 18 H, CH.sub.3), 2.2 (s, 1 H, SH), 3.75 (q, 12 H,
CH.sub.2) .sup.13C NMR (75.48 MHz, CDCl.sub.3) .delta. 18.7
(CH.sub.3) 31.2 (CHS), 58.7 (CH.sub.2O); EI-MS (m/z) 355 (11%,
M.sup.+), 310 (4%, [M.sup.+-44 (M-OCH.sub.2CH.sub.3).sup.+])
EXAMPLE 3
Synthesis of Sulfonic Acid PMO Under Basic Conditions
[0057] 60.00 g (3.33 mol) H.sub.2O was mixed with 30.00 g of 30 wt
% NH.sub.4OH (0.53 mmol NH.sub.3) NH.sub.4OH and 2.00 g (5.48 mmol)
cetyltrimethylammonium bromide (CTABr) was added. The solution was
stirred for 5 minutes and then an ethanol (4 mL) solution of the
crude product from Example 2 (3.50 g) was added. A deep red
solution was obtained. 0.5 mL of 30 wt. % H.sub.2O.sub.2 was added
to the solution after 5 minutes and the solution turned to orange
red color after about 20 minutes. After aging at 80.degree. C. for
4 days, the desired sulfonic acid periodic mesoporous organosilica
(SAPMO) product was obtained.
[0058] The CTABr surfactant was extracted from the product using
solvent extraction in an HCl/methanol solution. 0.5 gm of the
as-synthesized SAPMO powder was stirred for 6 hr at 55.degree. C.
in a solution of 5 g (36 wt %) HCl/170 g methanol. The product was
then isolated on a Buchner funnel, washed with methanol and dried
in air.
[0059] The solvent-extracted product was characterized by X-ray
diffraction and .sup.13C CP-MAS NMR spectroscopy and the results
are shown in FIGS. 1(a) and 2 respectively.
[0060] With regard to FIG. 1(a), it will be seen that the X-ray
diffraction pattern shows one peak at a low 2-theta value
indicating the presence of an ordered mesoporous structure in the
product.
[0061] With regard to FIG. 2, the major peaks in the .sup.13C
CP-MAS NMR spectrum at chemical shifts of about 2 and 22 ppm
correspond to the (O.sub.3Si).sub.2CH.sub.2 and
(O.sub.3Si).sub.2CHSO.sub.3H carbons respectively. The former is
likely a result of either unreacted methylene carbons in the
residue precursor used to synthesize the SAPMO or due to some
cleavage of the organosulphonic acid group during self-assembly or
oxidation of the thiol PMOs. The peak at about 50 ppm observed in
the spectrum is probably due to some adsorbed OCH.sub.3 carbons
from methanol used for washing.
[0062] The peak corresponding to the organosulphonic carbons at 22
ppm remained intact even after titration with a base, NaOH, with
only a slight shift due to the formation of the sodium salt of the
sulphonate (.dbd.CHSO.sub.3.sup.-Na.sup.+) indicating that the
organosulphonic acid groups in the product were stable to mild
basic solutions. After subsequent hydrolysis and regeneration of
the acid sites, the peaks corresponding to the organosulphonic acid
groups were observed.
EXAMPLE 4
Synthesis of Sulfonic Acid PMO Under Acidic Conditions
[0063] 13.4 g (0.75 mol) H.sub.2O was mixed with 7.17 g HCl (36.5
wt. %, 71.7 mmol), stirred for 1 minute and 0.34 g (0.93 mmol)
CTABr was added into the solution and stirring continued for 30
minutes. Then an ethanol (4 mL) solution of the crude product from
Example 2 (1.75 g) was added into the surfactant solution at RT.
Stirring was continued for 30 minutes and then the solution was
aged at 80.degree. C. for 2 days. After the precipitate was
recovered, it was washed with large quantity of water and the
surfactant was extracted in HCl/MeOH solution as in Example 3.
About 0.3 g of the surfactant-extracted product was taken, mixed
with 200 mL water and 15 g H.sub.2O.sub.2 (30 wt. %) was added to
the solution and the mixture was stirred under nitrogen for 5 hrs.
The product was isolated by filtration.
[0064] The product was characterized by X-ray diffraction and
.sup.13C CP-MAS NMR spectroscopy and the results are shown in FIGS.
1(b) and 3(a) respectively. FIG. 3(b) shows the .sup.13C CP-MAS NMR
spectrum of the mesoporous material before oxidation with
H.sub.2O.sub.2. The peak at about 50 ppm observed in the spectrum
shown in FIG. 3(b) is probably due to some adsorbed OCH.sub.3
carbons from methanol used for washing.
EXAMPLE 5
[0065] Synthesis of Sulfonic Acid PMO Under Acidic Conditions
[0066] The process of Example 4 was repeated but with the ethanol
(4 mL) solution of the product from Example 2 (1.75 g) and 0.44 g
of H.sub.2O.sub.2 (30 wt. %) being added simultaneously to the
surfactant solution at RT. Stirring continued for 30 minutes and
the solution was aged at 80.degree. C. for 2 days. The X-ray
diffraction the resultant product is shown in FIG. 1(c), whereas
the .sup.13C CP-MAS NMR spectra of the product, after and before
oxidation, are shown in FIGS. 4(a) and (b) respectively. It will be
seen from FIG. 4 that the product of Example 5 seems to contain a
relatively larger amount of sulphonic acid groups as compared with
the products of Examples 3 and 4.
EXAMPLE 6
Synthesis of bis(triethoxysilyl)methylbromide
[0067] To the lithiated carbanion solution prepared in Example 1
above, a slight excess of bromine (1.5 g, 9.4 mmol) at -78.degree.
C. was added. The solution was stirred at -78.degree. C. for 30
minutes and then at RT for 2 hrs. The solvent was pumped off and
the product was further extracted with dry pentane. The residue was
distilled under vacuum resulting in
bis(triethoxysilyl)methylbromide (86% yield): boiling point
144-148.degree. C. at 0.04 mm Hg; .sup.1H NMR (300 MHz, CDCl.sub.3)
.delta. 0.55-0.58 (t, 1 H, CHSi), .delta. 1.18-1.23 (q,18H,
CH.sub.3) .delta. 2.89-2.92 (d, 2H, CH.sub.2Ph), .delta. 3.78-3.82
(t, 12H, CH.sub.2O), .delta. 7.17-7.20 (d, 2H, ArH), .delta.
7.36-7.39 (d, 2H, ArH); .sup.13C NMR (75.48 MHz, CDCl.sub.3)
.delta. 10.80 (CHSi), .delta. 18.46 (CH.sub.3), .delta. 29.47
(CHPh), .delta. 58.66 (CH.sub.2O), .delta. 130.84, 131.10 (CH
aromatic); EI-MS (m/z) 508 (5%, M.sup.+), 464 (100%,
[M.sup.+-44]).
EXAMPLE 7
Coupling of bis(triethoxysilyl)methylbromide with KHS.xH.sub.2O
solution
[0068] A 0.2 g (3.58 mmol) KHS.xH.sub.2O solution in anhydrous
ethanol was prepared and was dried with MgSO.sub.4. After
filtration, the solution was added dropwise under stirring into 1.5
g (3.58 mmol) of the bis(triethoxysilyl)methylbromide prepared in
Example 6. The solution turned yellowish and some precipitate was
observed. After stirring for 5 minutes, the supernatant was
isolated and used as a SAPMO precursor.
EXAMPLE 8
Synthesis of Sulfonic Acid PMO Under Acidic Conditions
[0069] The same surfactant solution used in Example 4 was prepared
and the precursor (1.75 g) obtained in Example 7 was immediately
added into the surfactant solution and the product was aged at
80.degree. C. for 4 days. The product was treated with 0.5 mL, 30
wt % H.sub.2O.sub.2 and, after thorough washing, the surfactant was
removed as in Example 3. The X-ray diffraction the resultant
product is shown in FIG. 1(d), whereas the .sup.13C CP-MAS NMR
spectra of the product, after and before oxidation, are shown in
FIGS. 5(a) and (b) respectively.
EXAMPLE 9
Coupling of bis(triethoxysilyl)methylbromide with Solution of
H.sub.2S/KOH
[0070] H.sub.2S gas was bubbled into a solution of 0.2 g (3.58
mmol) KOH in 2 mL of anhydrous ethanol. The resultant solution was
added dropwise under stirring at RT into 1.5 g (3.58 mmol) of the
bis(triethoxysilyl)methylbromide precursor prepared in Example 4.
The overall solution was used as a SAPMO precursor immediately
after preparation and without being filtered or distilled further
to avoid hydrolysis of the alkoxy groups in the presence of KOH
base and moisture.
EXAMPLE 10
Synthesis of Sulfonic Acid PMO Under Acidic Conditions
[0071] To the surfactant solution prepared in Example 4, 1.75 g of
the precursor of Example 9 and 0.44 g H.sub.2O.sub.2 were added
simultaneously. Stirring continued at RT for 30 minutes and after
which the sample was aged at 80.degree. C. for 4 days. The sample
was washed thoroughly and the X-ray diffraction pattern of the
resulting sample is shown in FIG. 1(e).
EXAMPLE 11
Synthesis of 1,1-Bis(triethoxysilyl)-4-butanethiol
[0072] To the carbanion solution of Example 1 cooled down to
-78.degree. C. in THF (100 mL), 1.00 g (9.05 mmol)
3-chloro-1-propanethiol was added over 2 minutes. Stirring
continued at -78.degree. C. for 30 minutes and then at RT for 24
hrs under nitrogen and the color of the solution turned faint
yellowish. Then the solvent was pumped off and the crude was
distilled to obtain 1,1-bis(triethoxysilyl)butyl-4-thiol (73%
yield), boiling point 72-78.degree. C./0.15 mm Hg; 'H NMR (300 MHz,
CDCl.sub.3) .delta. 1.21 (t, 18 H, OCH.sub.2CH.sub.3), 1.3 0 (s, 1
H, SiCH), 1.80 (s, 1 H, SH), 2.16 (dd, 2 H,
CH.sub.2CH.sub.2CH.sub.2) 2.81 (t, 2 H, CHCH.sub.2), 3.65 (t, 2H,
CH.sub.2SH), 3.82 (q, 12 H, OCH.sub.2CH.sub.3); .sup.13C NMR (75.48
MHz, CDCl.sub.3) .delta. -7.89 (CHSi), 18.26 (OCH.sub.2CH.sub.3)
31.63 (CHCH.sub.2) 35.28 (CH.sub.2CH.sub.2CH.sub.2), 43.18
(CH.sub.2SH), 58.38 (OCH.sub.2); El-MS (mlz) 413 (24.8, M.sup.+),
385 (16.6%, [M.sup.+-28 (M-CH.sub.2CH.sub.3).sup.+]), 355 (19.6%,
[M.sup.+-58 (M-OCH.sub.2CH.sub.3).sup.+]).
[0073] The 1,1-bis(triethoxysilyl)-4-butanethiol was used as in the
previous Examples to prepare sulfonate functionalized mesoporous
materials.
EXAMPLE 12
Coupling of [bis(triethoxysilyl)methyl]lithium with trimethylamine
sulphur trioxide complex
[0074] To the carbanion/THF solution of Example 1 (9.00 mmol), 1.25
g (9.00 mmol) (CH.sub.3).sub.3N.SO.sub.3 solid was directly added
at -78.degree. C. Then the solution was heated at 50.degree. C. and
its color started turning yellowish and after 3 hrs all the
(CH.sub.3).sub.3NSO.sub.3 dissolved. Stirring continued overnight
at 50.degree. C. and the color of the solution turned deep red. The
solvent was pumped off and a 9.0 mL, 1M HCl/ethanol (9.0 mmol HCl)
solution was added while the solution was stirred for 5 minutes.
The precipitate, lithium bis(triethoxysilyl)methyl sulfonate, was
isolated by filtration and the residue was used as a precursor to
prepare SAPMOs.
* * * * *